1. Technical Field
The embodiments herein generally relate to Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) systems, and, more particularly, to techniques for improving reception of signals in an ISDB-T system.
2. Description of the Related Art
In recent years, the wireless industry has seen explosive growth in device capability, especially in relation to mobile devices, such as cell phones, handhelds, gaming consoles, etc. Ever-increasing demand for computing power, memory, and high-end graphic functionalities has accelerated the development of new and exciting wireless services. In the last few years, multiple technologies have been proposed to address delivery of streaming multimedia to mobile devices.
Multimedia communications provide a rich and immediate environment of image, graphics, sound, text, and interaction through a range of technologies. An example of multimedia communication is streaming multimedia, which is primarily a delivery of continuous synchronized media data. The streaming multimedia is constantly received by, and displayed to, an end user while it is being delivered by a service provider. Multiple technologies such as ISDB-T, Terrestrial-Digital Multimedia Broadcasting (T-DMB), Satellite-Digital Multimedia Broadcasting (S-DMB), Digital Video Broadcasting—Handheld (DVB-H), and FLO (Forward Link Only) are used to address the delivery of streaming multimedia to mobile devices. These technologies have typically leveraged upon either third generation cellular/PCS or digital terrestrial TV broadcast technologies.
ISDB, as the name suggests, is used for digital transmission and reception of integrated services, such as television, audio and data services. ISDB includes a variety of transmission standards for broadcasting of satellite, terrestrial, and cable signals. The ISDB transmission system utilized for broadcasting terrestrial digital television signals is termed as ISDB-T.
The ISDB-T system is based on Orthogonal Frequency Division Multiplexing (OFDM). A number of OFDM segments may constitute a plurality of transmission bands in the ISDB-T transmission system. The ISDB-T system is enabled to individually set operating parameters of each OFDM segment, thereby enabling a formation of flexible channels. Furthermore, signals in the ISDB-T system are transmitted in the form of symbols having different number of bits based upon the modulation system being used. An OFDM frame consists of 204 symbols having a sufficient guard interval in between to prevent inter-symbol interference effects. Moreover, the ISDB-T system utilizes Moving Pictures Expert Group-2 (MPEG-2) video coding and MPEG-2 Advanced Audio Coding (AAC), thereby enabling a simultaneous transmission of audio, video, and data. The audio, video, and data may be multiplexed to form a single transport scheme for transmission to the receiver. Additionally, a Transmission Multiplexing Configuration Control (TMCC) signal is transmitted with the multiplexed data to other information such as channel segment configuration and transmission parameters.
Conventionally, the ISDB-T system features three transmission modes, referred to as Mode 1, Mode 2, and Mode 3. Each OFDM segment of the three modes has different number of carriers, thereby enabling the use of wide range of transmitting frequencies for the system. Additionally, the ISDB-T system may be utilized to provide high quality and reliable video, audio, and data broadcasting for fixed as well as mobile receivers. Accordingly, it is desirable to have a quality reception while the receiver is in motion. Further, to achieve good reception of ISDB-T signals at higher speeds, the receiver must estimate operating parameters of the transmission channel. One such operating parameter is maximum Doppler frequency, also known as Doppler spread. An estimation of the Doppler spread may enable “tweaking” of a tuned demodulator of the mobile receiver to achieve a better reception of the ISDB-T signal at higher speeds.